Dynamic Parameters Research Articles

Ambient Vibrations Test for Assessment of Horizontal Diaphragms in Historic Buildings

ABSTRACT The structural assessment of horizontal diaphragms in historic buildings turns out to be one of the most difficult aims and challenges in the field of Structural Health Monitoring (SHM). Indeed, characterising these macro-elements is important for the building structural behavior as a whole and, above all, for their horizontal stiffness role, which is very strategic with respect to vertical walls. The present research proposes a monitoring approach exclusively through ambient vibration tests (AVT) by using specific velocimeters and Operational Modal Analysis (OMA). The sensors, named tromographs, are wireless, very light, with compact design and integrated software, very easy to apply. They can be used as single stations and synchronized with similar devices. The aim of the research was to evaluate the overall reliability of this approach through the evaluation of experimental dynamic parameters, as well as the frequencies and modal shape. In detail, the first part of the investigation focused on the specific characteristics of Venetian floors. The second part is dedicated to present each floor and its specific test campaign. To better check the monitoring structural approach, the first floor is timber-made but reinforced with steel beams; the second investigated floor is entirely made of wood; the last is a combination between reinforced concrete and timber. In all cases the floors are clamped to masonry walls. The third part is dedicated to the discussion of results, both in comparison and individually, particularly with respect to the entity of the found experimental dynamic parameters. The final and conclusive part outlines the benefits and problems of the AVT-proposed methodology. Conclusions show good overall reliability of the methodology does not appear complex in process elaboration and is easy to use, although there is a critical aspect due to noise effects and an overly high sensitivity of the velocimeters.

Simultaneous Mapping of Bubbling Regimes and Thermal Layer During Direct Contact Condensation of Steam Using Gradients-Based Approach

Abstract Direct contact condensation experiments of steam in subcooled water are carried out for subcooling levels of ΔTsub= 20 °C, 30 °C, and 40 °C with a steam injection mass flux of 20 kg/m2 s. Rainbow schlieren deflectometry is employed to visualize the thermal gradients around the condensing steam bubble in a nonintrusive manner. For the chosen flow and subcooling conditions, the bubbling regimes observed are the steam bubble growth stage, the bubble receding stage, and the bubble collapse stage. Two-dimensional images captured during the process of bubble condensation using rainbow schlieren images are presented. The redistribution of color captured through the recorded images directly reflects the thermal gradients present in the test section. Qualitative interpretation of the recorded images reveals that the thermal gradient layer thickness around the condensing steam bubble increases during the growth and receding stages, before the complete breakup of thermal gradient layer at the bubble collapse stage. The local profiles of hue distribution in the direction normal to the thermal gradient layer indicate high temperature gradients in this narrow region. The hue values and the average thickness of the thermal gradient layer were found to be maximum for 40 °C subcooling level compared to the other cases. The rate of growth and thereby the collapse of the thermal gradient layer is slower for low subcooling levels and increases with higher subcooling values. To the best of the knowledge of the authors, this work is one of the first attempts to simultaneously capture the dynamical parameters of the condensing steam bubble as well as the associated thermal gradients field using a single imaging technique, thus making the experimental approach relatively simple and cost effective.

Aroma Compound Release from Starches of Different Origins: A Physicochemical Study

Sensory properties, particularly aroma, play a crucial role in consumers’ acceptance and perceived quality of food. The release and the perception of aroma compounds is affected by their interaction with nonvolatile ingredients of foods, such as proteins, lipids, and polysaccharides. These interactions, whether reversible or irreversible, significantly influence aroma retention and release. Starch, a common food constituent, has been found to interact with aroma compounds, impacting flavor dynamics through processes like complexation and encapsulation. In this study, reversed-flow gas chromatography (RF-GC) is employed for the estimation of the release behavior of polar (diacetyl) and non-polar (dl-limonene) aroma compounds from starches of various origins (corn, wheat, rice, and potato). The results show that aroma compound release is influenced by the matrix composition, environmental conditions, and physicochemical properties of both starch and aroma compounds. The temperature-dependent mass transfer coefficients and activation energies reveal the strong influence of polar and non-polar characteristics on aroma compound behavior. Additionally, significant variations in retention and release are observed based on the starch type and the type of bonds involved in aroma compound interactions, underscoring the critical role of thermodynamic and kinetic parameters in flavor dynamics.

Non-invasive prediction of atrial cardiomyopathy characterized by multipolar high-density contact mapping.

Atrial cardiomyopathy (AC) establishes links between atrial fibrillation (AF), left atrial (LA) mechanical dysfunction, structural remodeling, and thromboembolic events. Early diagnosis of AC may impact AF treatment and stroke risk prevention. Modern endocardial contact-mapping provides high-resolution electro-anatomical (EA) maps of the LA, thus allowing to display the myocardial substrate based on impaired signal amplitude and to characterize AC. Correlation of invasively assessed AC using a novel, multipolar mapping catheter (OCTARAY™, Biosense Webster, limited market release) and LA echocardiographic parameters could form the basis for a set of echo parameters for non-invasive prediction of AC. We retrospectively identified 50 adult patients who underwent primary pulmonary vein isolation (PVI) for paroxysmal or persistent AF between 08/22 and 05/23 fulfilling the selection criteria: (i) EA mapping with a novel multipolar mapping catheter (Octaray®); (ii) acquisition of voltage maps in sinus rhythm (SR) with ≥ 5000 points/map; and (iii) transthoracic echocardiography acquired in SR ≤ 48h before PVI. Exclusion criterion was previous LA ablation. We generated EA maps with two sets of upper voltage thresholds (0.2-0.5mV and 0.2-1.0mV) and assessed total LA low voltage area (LVA). As LVA thresholds for the classification of AC are not yet established, an unsupervised machine learning cluster analysis was performed using a Gaussian mixture model (GMM), and two groups of patients with mild and severe AC were identified. Based on these two groups, we selected echo parameters for further analysis by applying the Boruta algorithm. The predictive capacity of the selected parameters was evaluated using a support vector machine. The mean age of the studied sample (n = 50) was 63 ± 11years, 62% were men, 64% showed persistent AF, median CHA2DS2-VASc score was 2 (quartiles 1, 3), and NT-proBNP was 190 (71, 391) pg/ml. A median of 5771 (5217, 6988) points/map were acquired. GMM yielded clusters of mild AC (n = 28) and severe AC (n = 22). Median LVA was 0.6 cm2 (< 0.5mV) resp. 4.1 cm2 (< 1.0mV) in group mild AC and 6.9 cm2 (< 0.5mV) resp. 27.2 cm2 (< 1.0mV) in group severe AC. Several echocardiographic parameters differed between the groups of mild and severe AC: dynamic LA parameters (end diastolic LA reservoir strain: 24.5% (22, 29) vs 15% (12, 19), p < 0.001; LA reservoir strain at atrial contraction: 22% (19, 25) vs 15% (11, 18), p < 0.001, end diastolic LA contraction strain: 13% (8, 15) vs 7.5% (3, 13), p < 0.01) as well as LA end-systolic volume index to a´ ratio (LAVI/a': 297 (231,365) vs 510 (326,781), p < 0.01). Consistent distribution of NT-proBNP (mild AC: 125 (48,189) pg/ml, severe AC: 408 (254,557) pg/ml, p < 0.0001) and CHA2DS2-VASc score (mild AC: 1 (1-2), severe AC: 3 (3-4), p < 0.0001) served as proof of concept. Applying the selected echocardiographic parameters, the machine learning algorithm correctly identified both subgroups with a mean AUC of 0.9 (95% CI 0.83-0.99). At 12months, AF recurrence rate was 10.7% in mild AC and 40.9% in severe AC (p < 0.05). Among patients qualifying for PVI, machine learning analysis of high-resolution LA maps allowed to identify subgroups with mild and severe AC avoiding the use of arbitrary LVA thresholds. The subgroups were predicted non-invasively with good accuracy using a machine learning approach that incorporated a set of echocardiographic markers. This data could advance the clinical triage of patients with AF.

Multiple TMDS Coupled with Viscous Dampers to Improve Acceleration Performance and Robustness of Buildings Subject to Wind-Induced Vibrations

The performance of a novel configuration of multiple tuned mass damper (MTMD) proposed by the author for floor acceleration reduction of linear elastic buildings subjected to broad-band wind force excitation is studied. To improve efficiency and robustness under variations or uncertainties of main-structure dynamic parameters, three single degree of freedom mass dampers in parallel are tuned to different frequencies close to the natural frequency of the target mode of vibration of the main structure and the classical viscous damping elements that connect the TMDs to the main structure are replaced by dampers that connect the masses of the TMDs. This special coupling between parallel TMDs is called viscous-coupling multiple tuned mass dampers (VCMTMD). The effectiveness of the proposed technique is evaluated and compared with conventional TMD and uncoupled MTMD configurations for the same total mass of the TMDs. The reduction of root mean square acceleration and deformations of the main structural system subjected to broad-band excitation is analyzed and compared with those of a conventional optimal TMD and of a parallel MTMD without coupling. The VCMTMD outperforms both the conventional TMD and parallel MTMDs in terms of deformation and acceleration reduction of the structure with the proposed TMD viscous coupling. The VCMTMD shows high robustness to changes or uncertainties in main-structure parameters (mass or stiffness). The proposed TMD configuration can find practical applications in wind-induced acceleration reduction in high-rise buildings and vibration reduction in different structures subjected to broad-band loading.

Crowding distance and IGD-driven grey wolf reinforcement learning approach for multi-objective agile earth observation satellite scheduling

ABSTRACT With the rise of low-cost launches, miniaturized space technology, and commercialization, the cost of space missions has dropped, leading to a surge in flexible Earth observation satellites. This increased demand for complex and diverse imaging products requires addressing multi-objective optimization in practice. To this end, we propose a multi-objective agile Earth observation satellite scheduling problem (MOAEOSSP) model and introduce a reinforcement learning-based multi-objective grey wolf optimization (RLMOGWO) algorithm. It aims to maximize observation efficiency while minimizing energy consumption. During population initialization, the algorithm uses chaos mapping and opposition-based learning to enhance diversity and global search, reducing the risk of local optima. It integrates Q-learning into an improved multi-objective grey wolf optimization framework, designing state-action combinations that balance exploration and exploitation. Dynamic parameter adjustments guide position updates, boosting adaptability across different optimization stages. Moreover, the algorithm introduces a reward mechanism based on the crowding distance and inverted generational distance (IGD) to maintain Pareto front diversity and distribution, ensuring a strong multi-objective optimization performance. The experimental results show that the algorithm excels at solving the MOAEOSSP, outperforming competing algorithms across several metrics and demonstrating its effectiveness for complex optimization problems.

Acute effects of voluntary breathing patterns on postural control during walking.

Breathing and postural control is reported to be both neuromuscularly and mechanically interdependent. To date, the effects of voluntary abdominal and thoracic breathing (VAB and VTB) on the EMG activity of muscles involved in both respiratory and postural functions, as well as gait biomechanics related to these breathing patterns, have not been investigated in young, healthy adults. The aim of the study was to evaluate the EMG responses of neck and trunk muscles, as well as the kinematic, stability, and kinetic parameters of gait induced by VAB and VTB compared to involuntary breathing (INB). Twenty-four healthy, physically active participants (12 men and 12 females) were required to complete three two-minute walking sessions on an instrumented treadmill (e.g. devices with capacitive sensors embedded beneath the running belt) at 5.0kmh-1, first with INB and then alternatively with VAB and VTB. A respiratory inductive plethysmography unit was used to provide real-time visual feedback of the breathing pattern performed by each participant. The EMG activity of the sternocleidomastoid (SCM), upper trapezius (UT), thoracic and lumbar erector spinae (TES and LES), as well as spatiotemporal (step width, stride length, stride time, stance phase, swing phase, and cadence), stability (anteroposterior and mediolateral center of pressure trajectory), and dynamic gait parameters (vertical ground reaction forces, vGRF) were recorded during each testing condition. Our findings revealed that both voluntary breathing patterns significantly affected the EMG activity of the SCM (p<0.01) and UT (p<0.05), with the activity between these muscles, as expressed by the SCM:UT ratio, being more balanced during VAB (0.94) and VTB (1.05) compared to INB (0.73). Additionally, VAB walking led to a narrower step width (p<0.01) and reduced vGRF over the forefoot (p<0.01) compared to INB walking. Neither VAB nor VTB influenced the activation levels of the LES and TES, nor did they affect other spatiotemporal, stability, or dynamic gait parameters (p>0.05). Our findings suggest that certain gait parameters (e.g. step width, forefoot vGRFs) are primarily influenced by VAB compared to INB, likely due to the more balanced activation of the SCM and UT muscles. This balanced activation may enhance head stability and control during walking, thereby contributing to improved postural control.

Dynamic wheel–rail adhesion characteristics on wet curved tracks considering surface roughness

Wheel–rail rolling contact is a complex tribological issue, especially the existence of a thin water film on the rail surface, which leads to low adhesion problems for the traction and braking performance of the railway trains. The objective of this paper is to propose a non-Hertzian dynamic wheel–rail adhesion model for trains passing through wet curved tracks considering wheel–rail surface roughness. A vehicle-track coupling dynamics model was first developed to output the wheel–rail dynamic contact parameters under wet conditions. These parameters were subsequently utilized as dynamic inputs for the present wheel–rail adhesion model to simulate dynamic curve passing. The present numerical model includes the normal contact model and tangential model. For the normal contact issue, an elastohydrodynamic lubrication model was used to accurately determine the normal contact stress within the contact patch along the contact traces. Based on the normal contact characteristics, the advanced extended creep force model was used to compute the tangential stress. Finally, the dynamic wheel–rail adhesion coefficient can be obtained. This model considers the effects of time variation and changes in contact geometry, resulting in sudden increases or decreases in the adhesion coefficient at certain locations. At a speed of 400 km/h, a higher spin creepage occurs, leading to an increased displacement of the third-body layer and causing the maximum tangential stress to shift from one side of the contact patch to the other. Under the combined influence of the creepages, the maximum tangential stress occurs at the trailing edge of the contact patch.

Active control of cavity buffeting noise using a DBD plasma model based on interval uncertainty correction

This study established a corrected system for a dielectric barrier discharge plasma actuator (DBD-PA) model and applied the corrected plasma model in research on the control of vehicle buffeting noise. Firstly, experiments on static ion wind characteristics under different excitation voltages were conducted, and the spatial distribution of the body force vector field during actuator operation was estimated. Subsequently, on the basis of experimental index parameters, an interval uncertainty multi-objective optimization (IUMOO) algorithm was used to reconstruct the expression of charge density and the action area boundary of the core electric field force, making them consistent with experimental results. A DBD-PA was arranged upstream of the cavity opening in the reverse direction, and experimental and numerical simulation results showed that noise reduction by this control scheme exceeded 3.67 dB at the characteristic wind speed. Finally, on the basis of the corrected plasma model, the correlation between vortex impact and pressure feedback in the buffeting phenomenon was analysed, and the influence of shear layer dynamic flow parameters on cavity buffeting noise was quantified. Results indicate that the DBD-PA acts to control the flow evolution of vortex cores and pressure clusters, suppress vortex reconnection, and weaken the intensity of vortex impact, thereby reducing wind buffeting noise.

Neutronic design and analysis of the accident-tolerant fuel (ATF) application to VVER-1000 nuclear reactor as well as evaluation of dynamic parameters

Neutronic design and analysis of the accident-tolerant fuel (ATF) application to VVER-1000 nuclear reactor as well as evaluation of dynamic parameters

Time-Varying Spatial Propagation of Brain Networks in fMRI Data.

Spontaneous neural activity coherently relays information across the brain. Several efforts have been made to understand how spontaneous neural activity evolves at the macro-scale level as measured by resting-state functional magnetic resonance imaging (rsfMRI). Previous studies observe the global patterns and flow of information in rsfMRI using methods such as sliding window or temporal lags. However, to our knowledge, no studies have examined spatial propagation patterns evolving with time across multiple overlapping 4D networks. Here, we propose a novel approach to study how dynamic states of the brain networks spatially propagate and evaluate whether these propagating states contain information relevant to mental illness. We implement a lagged windowed correlation approach to capture voxel-wise network-specific spatial propagation patterns in dynamic states. Results show systematic spatial state changes over time, which we confirmed are replicable across multiple scan sessions using human connectome project data. We observe networks varying in propagation speed; for example, the default mode network (DMN) propagates slowly and remains positively correlated with blood oxygenation level-dependent (BOLD) signal for 6-8 s, whereas the visual network propagates much quicker. We also show that summaries of network-specific propagative patterns are linked to schizophrenia. More specifically, we find significant group differences in multiple dynamic parameters between patients with schizophrenia and controls within four large-scale networks: default mode, temporal lobe, subcortical, and visual network. Individuals with schizophrenia spend more time in certain propagating states. In summary, this study introduces a promising general approach to exploring the spatial propagation in dynamic states of brain networks and their associated complexity and reveals novel insights into the neurobiology of schizophrenia.

Effect of field‐induced dynamic parameters on the electric field distortion characteristic of high voltage oil‐immersed bushing

Effect of field‐induced dynamic parameters on the electric field distortion characteristic of high voltage oil‐immersed bushing

Relationship between left ventricular contractile reserve and vector flow mapping analysis in chronic aortic regurgitation

Abstract Background When determining the optimal timing of surgery for aortic regurgitation (AR), evaluation of left ventricular contractile reserve (LVCR) using exercise stress echocardiography (ESE) is helpful. However, no previous studies have identified the relationship between LVCR and low energy efficiency in the left ventricle during exercise. Purpose We assessed the relationship between LVCR and the intraventricular flow dynamic parameters using vector flow mapping (VFM) in patients with chronic AR. Methods We retrospectively enrolled 44 consecutive asymptomatic or equivocally symptomatic patients undergoing ESE with more than moderate to severe chronic AR and a left ventricular ejection fraction (LVEF) of ≥50%. The patients were classified into two groups: ΔLVEF (peak workload − baseline) of ≥5% (LVCR(+)) and ΔLVEF of &amp;lt;5% (LVCR(−)). In the VFM analysis, energy loss (EL) and wall shear stress (WSS) were evaluated at baseline, low workload, and peak workload during exercise. Results Among the 44 patients, 32 were LVCR(−) and 12 were LVCR(+). At baseline, no differences were revealed in interventricular EL and WSS between the two groups. During exercise, however, EL was higher in patients with LVCR(−) than LVCR(+) [16.2 (11.7–22.5) vs. 11.2 (9.3–15.6) mW/m, p=0.015 at low workload; 17.8 (15.4–22.3) vs. 13.3 (9.6–18.0) mW/m, p=0.027 at peak workload]. EL at low workload could predict patients with LVCR(−) (odds ratio: 1.18, 95% confidence interval: 1.02–1.37, p=0.025). No differences in WSS were shown between patients with LVCR(−) and LVCR(+) during exercise. Conclusions In patients with chronic AR and LVCR(−), EL during exercise increased, and evaluation of EL at low workload was useful for predicting impaired LVCR. Impaired LVCR may be attributed to not only a non-physiological regurgitant jet but also increased cardiac work due to subclinical LV damage. Measurement of EL and WSS Changes in EL and WSS

Unveiling Lipid Droplet Transport Dynamics as Biomarkers of Senescence Using Label-Free, Time-Lapse Holotomography.

Accumulation and density of lipid droplets (LDs) in cells have been identified as a potential biomarker to detect senescent cells. However, their intracellular dynamic transport and alterations during senescence remain largely unclear. To address this knowledge gap, senescence was induced in human microglia cells using hydrogen peroxide (H2O2) to investigate both short-term and long-term effects of H2O2 treatment on LD dynamics. We captured time-lapse holotomograms of LDs using label-free refractive index (RI)-based holotomography and quantified 11 dynamic parameters of LDs through single-particle tracking. These quantified parameters were then compared across healthy cells, short-term H2O2-treated pre-senescent cells (H2O2-treated cells), and long-term H2O2-induced senescent cells (senescent cells). The results revealed that LD dynamics are significantly altered in both H2O2-treated pre-senescent cells and H2O2-induced senescent cells, though with differing trends. Healthy cells exhibited higher values in all LD dynamic parameters compared to senescent cells, with the exception of the mean directional change rate, which is lower. In addition, H2O2-treated cells showed higher values in dynamic parameters such as total displacement, mean straight-line velocity, and confinement ratio compared to healthy and senescent cells, due to the observed linear migration of LDs during H2O2 treatment. We found that the altered movement of LDs is closely related to H2O2-induced damage to microtubule networks. These findings suggest that altered LD dynamics, along with associated molecules and pathways, may serve as potential biomarkers for identifying senescent cells, thereby aiding in the development of novel therapeutic targets and senolytics.

The outer structure of old star clusters in the Small Magellanic Cloud

Abstract We report results on the internal dynamical evolution of old star clusters located in the outer regions of the Small Magellanic Cloud (SMC). Because the SMC has been imprinted with evidence of tidal interaction with the Large Magellanic Cloud (LMC), we investigated at what extend such an interaction has produced extra tidal structures or excess of stars beyond the clusters’ tidal radii. For that purpose, we used the Survey of the Magellanic Stellar History (SMASH) DR2 data sets to build number density radial profiles of suitable star clusters, and derived their structural and internal dynamics parameters. The analysed stellar density profiles do not show any evidence of tidal effects caused by the LMC. On the contrary, the Jacobi volume of the selected SMC star clusters would seem underfilled, with a clear trend toward a smaller percentage of underfilled volume as their deprojected distance to the SMC centre increases. Moreover, the internal dynamical evolution of SMC star clusters would seem to be influenced by the SMC gravitational field, being star clusters located closer to the SMC centre in a more advanced evolutionary stage. We compared the internal dynamical evolution of SMC old star clusters with those of LMC and Milky Way globular clusters, and found that Milky Way globular clusters have dynamical evolutionary paths similar to LMC/SMC old star clusters located closer to their respective galaxy’s centres. Finally, we speculate with the possibility that globular clusters belonging to Magellanic Clouds like-mass galaxies have lived a couple of times their median relaxation times.

Dynamic structural characteristics and vibration susceptibility of Tongren loess under the influence of water content and confining pressure

Loess is extensively developed on both sides of the Longwu River, a tributary of the Yellow River, Tongren County, Qinghai Province. The engineering geological characteristics are complex, and landslide disasters are highly developed. Based on field geological surveys and physical property analysis of the loess in this area, this study analyzes the influence of water content, consolidation pressure, and soil disturbance on the dynamic characteristics of loess using GDS dynamic triaxial tests. The results show that Tongren loess has strong structural properties. Its dynamic constitutive relationship conforms to the Hardin-Dinevich hyperbolic model, where the parameters a and b decrease with increasing confining pressure and increase with increasing water content. The dynamic cohesion and dynamic friction angle both decrease with increasing water content, with the dynamic cohesion significantly affected, decreasing by 77% ~ 83% when saturated. However, the dynamic friction angle is less affected by water content changes, decreasing by 18% ~ 25% when saturated. Under dynamic conditions, the dynamic friction angle of Tongren loess is only 12 ~ 16°, making slopes composed of Tongren loess highly susceptible to instability and sliding under strong earthquake conditions. The dynamic structural properties of Tongren loess are significantly influenced by water content, with increasing water content destroying the joint structural strength of intact loess. Before reaching the plastic limit water content, the joint structural strength of intact loess decreases sharply with increasing water content, and then decreases slowly. The frictional structural strength shows an opposite trend. Under the same experimental conditions, the failure dynamic stress, maximum dynamic elastic modulus, and dynamic shear strength parameters of intact loess are generally greater than those of remolded loess, and the differences between them decrease with increasing water content. This study provides insights into the dynamic structural characteristics of Tongren loess, which can serve as a reference for understanding the formation mechanisms, stability analysis, and seismic design of loess landslides in the region.

Experimental–Analytical Method for Determining the Dynamic Coefficients of Turning Tools

The article presents an analytical and experimental method for determining the dynamic coefficients of cutting tools, with particular emphasis on turning tools. The method involves aligning the acceleration profile obtained from empirical investigations with a mathematical model describing the oscillations of the cutting tool tip. The stiffness (k) and damping (c) coefficients determined using this approach enable the design of tools with desired dynamic characteristics, tailored to specific machining processes, such as machining with long overhangs. From the perspective of mechanical dynamics, selecting appropriate stiffness and damping values allows for the design of tools with optimal dynamic properties. High stiffness reduces the occurrence of deformations under external forces, while adequate damping facilitates the rapid attenuation of vibrations, thereby minimising their adverse effects on the machining process. The developed method could serve as a practical tool for identifying the dynamic parameters applicable to a wide variety of cutting tools. The analysis includes three types of turning tools: one with a steel shank, another with a carbide-core steel shank, and a third with a carbon fibre-core steel shank. The results of the tests indicate that the E-A20Q SDUCL 11 tool is best suited for operations requiring high stability and minimal vibration, owing to its favourable damping and stiffness properties.

Sea Clutter Suppression Method Based on Ocean Dynamics Using the WRF Model

Sea clutter introduces a significant amount of non-target reflections in the echo signals received by radar, complicating target detection and identification. To address the challenge of existing filter parameters being unable to adapt in real-time to the characteristics of sea clutter, this paper integrates ocean numerical models into the sea clutter spectrum estimation. By adjusting filter parameters based on the spectral characteristics of sea clutter, the accurate suppression of sea clutter is achieved. In this paper, the Weather Research and Forecasting (WRF) model is employed to simulate the ocean dynamic parameters within the radar detection area. Hydrological data are utilized to calibrate the parameterization scheme of the WRF model. Based on the simulated ocean dynamic parameters, empirical formulas are used to calculate the sea clutter spectrum. The filter coefficients are updated in real-time using the sea clutter spectral parameters, enabling precise suppression of sea clutter. The suppression algorithm is validated using X-band radar-measured sea clutter data, demonstrating an improvement factor of 17.22 after sea clutter suppression.

Research on shale dynamic and static elastic modulus and anisotropy based on pressurization history

The dynamic and static elastic parameters of rocks exhibit differences. It is of great practical significance to carry out experiments on dynamic and static elastic parameters of rocks under reservoir conditions and determine the conversion relationship between dynamic and static elastic parameters. In this study, shale oil samples from the second member of Kongdong sag in Dagang Oilfield were analyzed by triaxial compression experiments at different bedding angles and longitudinal and shear wave velocity tests. Dynamic and static stiffness coefficient, elastic modulus and acoustic wave velocity change under different directions of pressure and pressure relief. The results indicate that the P-wave velocity, fast shear wave velocity, slow shear wave velocity, dynamic and static Young’s modulus exhibit an increase as the confining pressure rises, and the parameters are greater during the unloading process than during loading process. At identical confining pressures, the dynamic Young’s modulus measured by cores with parallel bedding plane is greater than that measured by cores with vertical bedding plane. The dynamic and static elastic mechanical parameters of different bedding angles can be transformed under varying pressures, and the dynamic elastic mechanical parameters measured under varying levels of confining pressure can be transformed into static elastic mechanical parameters under equivalent confining pressures, which offer fundamental parameters for examining rock mechanics properties and serving as a reference for developing fracturing construction plans for oil and gas reservoirs.

Global sensitivity analysis of high-speed train dynamics system with high-dimensional inputs and multiple outputs

A high-speed train dynamics system involves numerous uncertainty parameters, and there are multiple evaluation indices for its dynamic performance. In this paper, we conduct high-dimensional and multi-output global sensitivity analysis for the dynamic performance of high-speed trains by comprehensively considering these dynamics parameters and indices. Firstly, the dynamics simulation model of the high-speed train is established and six dynamics indices for evaluating the safety and comfort of the train are obtained under operating conditions. Subsequently, considering the multi-output and high-dimensional characteristics of train sensitivity analysis, we propose a multi-output global sensitivity analysis method based on the correlation-analysis-guided Kriging model (CA-K). Finally, global sensitivity analysis of 96 uncertainty parameters on six dynamics indices is conducted under three scenarios utilising the proposed method. The results show that (1) CA-K achieves higher accuracy in approximating high-dimensional train dynamics indices than existing conventional surrogate models. (2) The multi-output global sensitivity analysis method can simultaneously identify all important dynamics parameters and exclude unimportant parameters.